About 750 firefighters and water jettisoned planes fought the blaze in harsh conditions with high temperatures and strong winds.
“Thousands of people have been evacuated as a precaution, but there are no casualties,” a firefighter spokeswoman said on Tuesday, adding that the fire was “still very violent”.
France is the latest of a number of Mediterranean countries to be affected by extreme weather and forest fires, which climatologists say will become increasingly common due to man-made global warming.
The rapidly spreading fire, which started about 100 km (60 miles) from the Mediterranean city of Toulon on Monday, has already razed more than 3,500 hectares (8,600 acres) of forest and brushwood on Tuesday. morning, according to firefighters.
The evacuations mainly took place around Saint-Tropez and the villages of Mole and Grimaud.
The Var prefecture confirmed that several campsites had been cleaned and that residents were asked to avoid clogging the roads around the Gulf of Saint-Tropez so that the emergency services could access the area.
Forest fires have already broken out this summer around the Mediterranean basin, particularly in Greece, Turkey, Spain, Portugal, Algeria and Morocco.